emissions light on

[Jeffrey thomure]

ok so i have a 2007 ram 3500 mega cab 6.7L cummins ive had it a couple of years. i bought it to pull my 36 ft 5th wheel i put a 5th wh hitch in it and its ready to pull just about anything trouble is i haven't had to move it yet .and being a 1 ton dully it s 1 ruff riding SOB. Any who when i bought it the heater didn't blow any hot air so i pu;;ed the dash out and replaced 2 of 5 vent doors that had broken and heater cord and air condenser needless to say i still don't have heat will when i got it all back together the light for emissions came on i think thats the light that looks like a engine block knowing it wasn't on before i took the dash out i found where the air breather latches on was on correctly the light went off that ws a few months ago now its back on but where the milage on the dash is it says 'NO FUSE' ? and the onboard computer where the headliner maplights are when its time to be serviced is located it also doesn't come on even the sterio quit. i don't know if all are related to the same problem but there is no fuse or relay thats bad as far as i can tell its got me stumped on where to begin to find the problem , if anybodys has a answer i surely need some guidance on this one . Sorry so long just to get to the point. What ive read its not good to drive very long with that light on ! THANX IN ADDVANCE JEFF T. YUKON OK.